Detergent compositions manufactured in the form of tablets of compacted detergent powder are known in the art. U.S. Pat. No. 5,225,100, for example, describes a tablet of compacted powder comprising an anionic detergent compound which will adequately disperse in the wash water.
Although detergent compositions shaped as tablets have received much attention in the patent literature, the use of such tablets to provide a unit dose fabric softener which will soften or condition fabrics without impairing detergency is not known.
One possible option for providing a unit dose softener is to introduce the softening ingredients directly into the rinse cycle. But, for this type of product to be effective several practical requirements must be met. To begin with, the size and shape of the unit dose container must be readily compatible with the geometry of a wide variety of rinse cycle dispensers designed for home washing machines in order to insure its easy introduction into the dispenser.
Further, the unit dose composition must be formulated to readily dispense its contents upon contact with water in a period of time corresponding to the residence time of the unit dose in the dispenser, namely, the period of time during which water enters and flows through the rinse cycle dispenser. The aforementioned practical requirements have to date not been successfully met and therefore there remains a need in the art for a commercially acceptable unit dose softener capable of activation in the rinse cycle.
Wash cycle softeners are known in the art which condition fabrics during the period of the wash cycle. Tablet unit doses for detergent compositions are also known. Such tablets are typically flat compacted unit compositions which conceptually offer numerous advantages to the consumer such as: ease of dosing; cleaner wash cycle dispensers resulting from not being dosed with loose powder; less bulk to carry and dispense; ease of handling relative to liquids; and environmental benefits attendant to reduced packaging requirements.
But, despite these advantages. there is a major drawback which occurs in front loading washing machines which represent at least 90% of the European market, and are gaining in consumer acceptance in North America. In front loading machines, a flat compacted object when introduced into the wash cycle often becomes trapped within a few minutes in the rubber seal surrounding the window of the washing machine. Once trapped in the seal, the tablet tends to remain trapped until the wash cycle is over and is consequently not dispersed in the wash water. To overcome this problem, different approaches have been taken.
Some tablet manufacturers provide a net or sachet designed to contain the tablet unit dose, and thereby avoid the problem of direct contact between the tablet and the seal. Another proposed solution involves providing a rapidly dispersible tablet in the wash water by incorporating an effervescent matrix and/or a disintegration agent into the tablet. But, these proposed options are generally uneconomical and often result in an unduly fragile tablet unable to readily withstand normal handling by the consumer without fracturing. Thus, there is a need for an economical unit dose tablet capable of providing conditioning of fabrics, and which retains its physical integrity during normal handling prior to being introduced into the washing machine.